Organic synthesis reactions using metal complexes as catalysts have hitherto been utilized for many purposes. In particular, many reports have been made regarding asymmetric catalysts useful for asymmetric syntheses, such as asymmetric isomerization and asymmetric hydrogenation.
For example, in order to improve the performance of these catalysts, various phosphine compounds having a special structure have hitherto been developed as disclosed, e.g., in Kaqaku Sosetsu, Vol. 32, pp. 237-238, "Yuki Kinzoku Sakutai no Kagaku" (1982), edited by The Chemical Society of Japan and J. D. Morrison, Asymmetric Synthesis, Vol. 5, Academic Press, Inc. (1985). Among them, many complexes in which a chiral tertiary phosphine compound is coordinated to a metal, e.g., rhodium, ruthenium, and palladium, exhibit excellent performance as a catalyst for asymmetric synthesis. In particular, 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (hereinafter abbreviated as "BINAP") is one of the excellent phosphine compounds as described in JP-A-55-61937 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"). Further, it has also been reported that 2,2'-bis(diphenylphosphino)-6,6'-dimethyl-1,1'-biphenyl (hereinafter abbreviated as "BIPHENP") is an effective catalyst component in asymmetric hydrogenation as described in JP-A-63-135397.
The most commonly employed processes for synthesizing optically active carboxylic acids include a process comprising chemically oxidizing a naturally occurring optically active alcohol or aldehyde to obtain a corresponding carboxylic acid, a process comprising optically resolving a racemic carboxylic acid with an optically active amine, and a process comprising converting a racemic carboxylic acid to its ester and partially hydrolyzing the ester with the aid of an enzyme or a microorganism to obtain a desired carboxylic acid.
In addition, an optically active carboxylic acid can be obtained by asymmetric hydrogenation of an .alpha.,.beta.-unsaturated carboxylic acid in the presence of a chiral catalyst. In this case, satisfactory results may be obtained in the syntheses of some carboxylic acids but, in general, the choice of an optically active phosphine as a component of the chiral catalyst is of importance, and there have been developed only few chiral phosphine compounds that are applicable for general purposes.
In an attempt to develop a phosphine compound providing catalysts having excellent catalytic performance, the present inventors conducted extensive investigations on tertiary phosphine compounds having axial chirality. As a result, they found that 2,2'-bis(dicyclohexylphosphino)-6,6'-dimethyl-1,1'-biphenyl (hereinafter referred to as "BICHEP") represented by formula (I): ##STR2## significantly increases stereoselectivity in asymmetric synthesis, i.e., optical yield, as reported in Miyashita, et al., The 58th Springtime Annual Meeting of The Chemical Society of Japan, Lecture Preprint II, pp. 1492 (1989).